Blasting cartridge



Ffib, 9, 1943. J/BARAB 2,310,344

BLASTING CARTRIDGE Filed April 18, 194;

.L J Q FIG."I

JACOB BARAB INVENT OR.

BY wwl R. mm g,

Patented Feb. 9, i943 BLASTDTG CARTRIDGE .lacob lBarab,

Wilmington, Hercules Powder Company, a corporation of Delaware DeL,assignor to Wilmington, Del,

Application April 18, 1941, Serial No. 389,124

8 Claims.

This invention relates to an improved blasting cartridge and to methodsof production thereof. It relates more particularly to a blastingcartridge surrounded by a compressible admixture which provides acushioning action for the initial explosive shock.

It is the principal object of this invention to provide a blastingcartridge enclosed in a sheath comprising a compressible cushioningadmixture. A further object of this, invention is to provide a sheathcomprised of an admixture which is compressible and which contains aflame-quenching salt. A further object of this inventon is to provide acomparatively low density admixture which may be packed into a tubularsheath for use around an explosive cartridge.

A further object of this invention is to provide an explosive cartridgesurrounded by a comparatively low density, tubular sheath which willcushion the initial shock of the explosion. A still further object ofthis invention is to provide an explosive cartridge which is surroundedby a tubular sheath of compressible material that will give improvedblasting results in operations such as coal mining.

Other and further objects will be apparent hereinafter.

The cushioning of the initial shock of a blast- Eng explosion with acompressible, cushioning material in accordance with this invention isof particular importance for explosive cartridges subject to use inproducing high percentages of lump material such as is desired in coalmining. After the initial shock of the explosive has been absorbed bythe cushioning material, the expanding gases released by the explosionfurther expand, but without a shattering force, into the cleavage planesof the seam being blasted with a resulting pushing action which breaksup the structure in such a manner that large firm lumps are obtained.Without the cushioning material about the explosive, the shatteringforce causes a large amount of pulverized material to be produced. Inparticular, for example, lump coal brings higher prices and anyimprovement which will givea larger percentage of lump in any givenblast constitutes a highly desirable improvement in the blastingoperation necessary in coal mining.

The improvement in blasting cartridges described in accordance with thisinvention may be accomplished with any desired form of explosives, butwill be found most advantageous in connection with, for example, thedynamites developed for use in coa mining. The shattering effect of coalmining explosives, for example, the permissible dynamites, when fired indirect contact with coal, while not of the high order of that obtainedwith straight dynamites, is, nevertheless, undesirable. By sheathingthese explosives, especially the permissibles, a higher percentage oflump coal is obtained.

The improved explosive cartridge which provides the advantage relatedabove in the mining of lump coal may be produced in accordance with thepresent invention by surrounding an explosive cartridge with a sheathcomprising an admixture of diatomite, such as diatomaceous earth,kieselguhr, tripolite, infusorial earth and the like, a binder and aflame-quenching salt. The binders which I have found desirable for usewith the diatomite may be materials having adhesive properties ormaterial which form a matrix such as, for example, dextrin, clay, sodiumsilicate, waste sulfite liquor, wood pulp, such as kraft pulp or sulfitepulp, asbestos fiber, balsa, bagasse, and other similar bindingmaterials. The flame-quenching salt which I have found to be adaptablefor use in my admixture may be, for example, sodium bicarbonate, sodiumchloride, boric acid, ground gypsum, borax, cal cium chloride or thelike.

The admixture prepared in accordance with this invention may be formedinto a tubular sheath by packing it a substantially rigid tube so thatthe internal diameter thereof is equivalent to the diameter of theexplosive cartridge which is to be inserted within the tubular member.The formed sheathing will be semi-rigid and have a cellular, favosestructure. The packing of the material may be accomplished by machinessuch as, for example, described in the co-pending application of R. B.Smith and K. Wassen, Serial No. 273,301, filed May 12, 1939.

Having now indicated in a general way the nature and purpose of thisinvention, there follows a. more detailed description of preferredembodiments thereof with reference to the accompanying drawing in whichFig. 1 represents a cushioning sheath partially in section andcontaining an explosive cartridge, and Fig. 2 is a view of thecushioning sheath of Fig. l, on line 2-2.

Referring now to the drawing, the assembled article of this inventioncomprises a blasting cartridge l surrounded by a cushioning sheath 2comprising a packed, homogeneous material 3 retained in position by asurrounding tube 4. The explosive cartridge I comprises an explosiveinto an annular ring within composition wrapped in paper t which iscrimped i at the end.

If desirable, a cap 8 may be placed over either or both ends of theassembly. The cap will be found desirable when a unitary explosurecharge is manufactured. The cap may be placed on the end of thecushioning sheath as shown in Fig. l and either be composed of a sheetof material such as cardboard or the like or composed of thecompressible admixture 3" which surrounds the explosive cartridge. If itis desirable, the cap may be formed in the shape of a plug and insertedin the end of the sheath 2 proper. In such instances the sheath 2 willbe slightly longer than the explosive cartridge which is to be used. Theplug may be retained by any adhesive, taping or similar emedient.

The thickness of the cushioning material may be varied to providevarying amounts of cushioning effect. A thickness of about A; to aboutinch is desirable for most purposes. Thus, a sheath to fit around a 1%by 8 inch dynamite cartridge will be about 1% inches, inside diameter,and about 1 inches to about 1 inches outside diameter. This sheath may,of course, be about the same length as the cartridge and oepn on bothends in order to aid propagation of the explosive, or the ends of thecartridge may be closed with caps or plugs described hereinbefore, andmade either of cardboard or of the sheathing composition. The closing ofthe ends of the cartridge slightly retards the-propagation of detonationfrom one cartridge to another, but, when only one cartridge is to beused in the explosion, the closed end sheath is desirable.

The diatomite which is found preferable for use in the sheath of thisinvention is known by many names in the industry and is produced inmanysections of the country.

In the specification and claims, the term diatomite is here used in itsgenerally accepted sense, i. e., diatomite is the name now generallygiven to a mineral substance composed of the tiny skeletal remains ofdiatoms which are microscopic, fiowerless, water plants related to thealgae. This residuum diatomite is essentially hydrous amorphous silica.

Common names for diatomite are: Diatomaceous earth, tripolite,kieselguhr, and infusorial earth, Strictly speaking, however, the lattermaterial is not truly a diatomite, as it is composed of the fossilremains of infusoria, which usually do not occur with the diatomaceae.Other synonyms for diatomite are: Diatomaceous silica, kieselmehl,bergmehl, diatomeenpeelite, polirschiefer,'moler, molera, molererde,desmid earth, fossil flour, mountain flour, farine fossil, white peat,radiolarian earth, chalk rock, ceyssatite, randanite, and tellurine;also various diatomite products of individual companies are known bytheir own trade names.

The sheathing in accordance with this invention may comprise as high asabout 50% diatomite, but will preferably contain between about 30 andabout 40% diatomite with the remaining percentage comprising a flamequenching salt and minor amounts of binder. The sheaths found mostdesirable for commercial use are composed of an admixture of 35%diatomite, 65% sodium bicarbonate with just sufiicient dextrin binder toform a packable composition whichiipon drying will not crumble.

In order to illustrate the various preferable embodiments of theinvention, the following examples are given.

Erample I sheaths were made from the following admixture: 600 pts.sodium bicarbonate, 00 pts. diatomite, 400 pts. sodium silicatesolution- 1 part in 12 parts of water by packing into a spiral-woundpaper tube. The total amount of water present will be coordinated togive most desirable packing properties. The wall thickness of the packedsheaths was 0.233" and the average weight of a 1%" x 8" sheath,exclusive of the paper tube, was approximately 115 g. Similar sheathscomposed of only sodium bicarbonate and a dextrin binder weighed 154 g.The apparent densities of the two types of sheaths were 0.79 g./cc. and1.05 g./cc. respec tively.

Ercample II sheaths were made from the following composition: 700 pts.sodium bicarbonate, 300 pts. diatomite, 250 pts. dextrin binder.

This composition produced a sheath for a 1% x 8" explosive cartridgewhich had a dry weight of 125 g. with a wall thickness of approximately0.23 and a density of 86 g./cc. The dextrin binder used was prepared bymaking an aqueous solution containing about 6-8% dextrin and 2-3% borax.If desired and in order to facitate packing, the binding solution may befurther diluted, or in some instances, it may be used in a moreconcentrated form. The borax was added as a preservative but is notessential.

Example II I sheaths were made from a composition comprising 650 partsof sodium bicarbonate and 350 parts of diatomite in which the amount ofbinder was varied over a wide range. had a dry weight of 120 g. and adensity of 82 g./cc. The amount of binder was not essential. however,small amounts of binder produced sheaths which had a tendency to crumblewhile excessive binder made the admixture difficult to pack.

The two sheaths described in Examples I and II, after being dried, werecrushed in a hydraulic press to determine their strength. The method wasto place the sheaths between two saddles 1 inch wide and apply hydraulicpressure until inch movement took place. On this test the crushingstrength of the sheaths was about to pounds which is sufiicient strengthto withstand handling, packing, and shipping.

The advantages of the sheaths of this invention are that they are veryeasily manufactured, since the admixtures pack easily and dry quickly.Further, the ingredients are economically and easily obtainable in allsections of the country and do not require expensive processing.Further, it has been found that the strength of the sheaths produced ishigh enough so that sheathing may be prepared at an explosive plant andshipped without insertion of a support within the tube. The sheathingsmay be shipped in normal cases, and, upon arriving at the destination,are not broken or crushed. The possibility of shipping sheaths withoutsupports within the tube allows a reduction of freight rates and doesaway with the necessity of removing the supports whenever the tubesareto be used. Of course, it is possible to ship the sheath aroundexplosive cartridges, but in doing this, the freight rates are muchhigher since explosive materials carry premium freight rates. Likewise,it is oftentimes desirable to use explosive The cartridge 7 cartridgeswithout the sheath around the car-. tridge,.especially when overburdenof slate must be broken out of the way to contact the coal face. Byshipping the sheath and explosive cartridges in separate containers, itis possible to use one type explosive within a mine, and this isadvantageous since the fewer materials there are to be isolated, themore efiicient the operation of the mine becomes.

It will be appreciated'that the above details and examples are givenmerely for the purpose of illustrating my invention andare not intendedto limit the invention. Moreover, many variations in the compositionsand procedures employed may be made without departing from the scope ofthe invention.

The present application is a continuation-inpart of my applications,Serial 'Nos. 225,342, now U. S. Patent No. 2 ,227,059, and 345,712,filed August 17, 1938, and July 16, 1940, respectively.

What I claim and desire to protect by Letters Patent is:

1. An improved blasting assembly including an explosive cartridgesurrounded by a preformed, annular, tubular sheath comprising betweenabout 30% and about 50% diatomite, and a flame-quenching salt, saidsheath characterized by a semi-rigid, cellular, favose structure whichis adapted to provide a cushioning action for the initialexplosiveshock.

2. An improved blasting assembly including an explosive cartridgesurrounded by a preformed, annular, tubular sheath comprising betweenabout 30% and about 50% diatomite, a binder, and a flame-quenching salt,said sheath characterized by a semi-rigid,'cellular, favose structurewhich is adapted to provide a cushioning action for the initialexplosive shock.

3. An improved blasting assembly including an explosive cartridgesurrounded by a preformed, annular, tubular sheath comprising betweenabout 30% and about 50% diatomite, a matrix, and a flame-quenching salt,said sheath characterized by a semi-rigid, cellular, favose structurewhich is adapted to provide a cushioning action for the initialexplosive shock.

4. An improved blasting assembly including an explosive cartridgesurrounded by a preformed, annular, tubular sheathycomprising betweenabout 20% and about and a flamequenching salt, said sheath characterizedby a semi-rigid, cellular, favose structure which is adapted to providea cushioning action for the initial explosive shock.

5. An improved blasting assembly including an explosive cartridgesurrounded by a preformed, annular, tubular sheath comprising betweenabout 30% and about 50% diatomite and sodium bicarbonate, said sheathcharacterized by a semi-rigid, cellular, favose structure which isadapted to provide a cushioning action for the initial explosive shock.

6. An improved blasting assembly including an explosive cartridgesurrounded by a preformed, annular, tubular sheath comprising betweenabout 30% and about 50% diatomite, dextrin, and a flame-quenching salt,said sheath characterized by a semi-rigid, cellular, favose structurewhich is adapted to provide a cushioning action for the initialexplosive shock.

7-. An improved blasting assembly including an explosive cartridgesurrounded by a preformed, annular, tubular sheath comprising betweenabout 30% and about 50% diatomite and wood pulp, and a flame quenchingsalt, said sheath characterized by a semi-rigid, cellular, favosestructure which is adapted to provide a cushioning action for theinitial explosive shock.

8. An improved blasting assembly including an explosive cartridgesurrounded by a preformed, annular, tubular sheath comprising betweenabout 30% and about 50% diatomite, sodium bicarbonate, and dextrin, saidsheath characterized by a semi-rigid, cellular, favose structurewhich isadapted to provide a cushionin action for the initial explosive shock.

JACOB BARAB.

